Organo-polysiloxanes



Patented May 10, 1949 UNITED. STATES PATENT or fice 2,469,888ORGANO-POLYSILOXANES Winton I. Patnode, Schenectady, N. Y., asaignor toGeneral Electric Company,

New York No Drawing.

in which the various R's represent the same or different lowermonovalent hydrocarbon radicals selected-from the class consisting oflower alkyl, aryl, alkaryl, and aralkyl radicals, examples of which arethe methyl,. ethyl, propyl, phenyl, benzyl, tolyl, xylyl, etc. radicals,and a is a whole number and is equal to at least 3. Preferably themajority of the HS represent methyl groups when the resulting compoundsare used as lubricants.

The term "polysiloxane as used herein refers to the fact that thecompounds so designated have a skeletal structure of alternate atoms ofsilicon and oxygen. The structure may be either of the straight orbranched chain type. A type formula for the linear or straight chaincompounds falling within the scope oi'this invention is R R i where thevarious Rs have the same significance as noted above, and n is aninteger equal to at least one.

A type of formula for the simpler branched chain type of compound is R RR 'ni o-sii o-si-a where R and n have the same significance as notedabove.

As an example of the more complex type of a corporation of ApplicationOctober 29, 1942, Serial N0. 463,814

branched chain polysiloxane falling within the scope of this invention,the following is given:

a n R--Ji-R n st-n R R n a-s1-ob-o-sl-o-slr-o-sil-o-ai-n R- i-R a-si-nThe scope of the invention is further and specifically defined, and thecompounds falling within it are distinguished from all other knownorgano-silicon compounds, by the following cri-. teria:

1. Each silicon atom is joined to at least one other silicon atomthrough an oxygen atom.

2. Oxygen atoms are found only between silicon atoms.

3. The ratio of the number of R groups to the number or silicon atoms isfixed and is equal to em a where a is the number of silicon atoms.

4. Each terminal silicon atom of the skeletal structure is joineddirectly to three R groups.

Thus it is seen that although the number of individual compounds comingwithin the .scope of the invention is large, the class of compounds isnarrowly defined by these four criteria. Since all of the compoundsdefined by the four criteria have the general formula wherein R and ahave the meanings herelnbefore indicated, the oxygen to silicon ratioofthe individual compounds or mixtures thereof I 3 I is equal to at leasti: e. at least 0.68, and is always less than 1.

Examples of specific chemical compounds included in this classificationare: 7

1. Octgniethyltrisiloxane (CI-IaMSi-O-SKCHsh-O-SKCI-h):

2. Decamethyltetrasiloxane l 3. Dodecamethylpentasiloxane (CeHtCHs)aSl-OSi(CeHsCHa) O-S1(CeHeCH2) a 8. Methyl tri-(trimethylsiloxy) silanecHmsi-o-ss-o-suom sucnoi 9. Dimethyl tetra-(trimethylsiloxy) disiloxane(011m AKCHOI l0. Symmetrical l,3-hexaphenyl-2-dimethyltrisiloxang.

(ctnsiksi-o-sucnm-o-suctmn 11. symmetrical 1,3-hexamethyl-2-diphenyltri-4 siloxane (CH1) 3Si-OS1(CeHa) :OSi(CI-L1) a 12.1,3-hexamethyl-2-methyl-2-phenyltrisiloxane (CH3) aSiOS1(CI-I3) (CeHt)O-Si(CI-Ia) a In the system of nomenclature adopted in naming the abovecompounds, the individual silicon atoms in the Si-O-Si chain have beendesig-' nated by numerals, the 81-0 group in which the oxygen isconnected to a second silicon atom has been called a "siloxy group, andthe compound containing them a siloxane. On this basis the compoundHaSi-O-iHa is known as disiloxane with the prefix indicatingthe numberof silicon atoms in the chain. The system resembles somewhat the Genevasystem of nomenclature of organic compounds.

The novel compounds of my invention are useful for diverse purposes. Forexample, they may be used as intermediates in the preparation of othercomplex silicon compounds. They may also be used as plasticizers orsofteners for various resins, including the silicone resins such asthose described and claimed in Patents 2,258,218-222 issued to Eugene G.Rochow. 70

Liquid mixtures of the various compounds represented by the typeformulas may also be used as electrical insulating fluids, dampingfluids. etc. Such mixtures are particularly useful as inafter. Morecomplex or resinous silicon compounds may be prepared by treating mycompounds in such a manner as to oxidize one or more of the hydrocarbonradicals to form com-' pounds capable of further condensation with oneanother. The more viscous materials may be used as waterproofimpregnating agents by application from solution. I

The preferred process employed in the preparation of the novelpolysiloxane derivatives briefly comprises treating a mixture of anorgano. disiloxane having the general formula RaSi-O-SlR:

and a silicone or polysiloxane having the general formula wherein a: isnot greater than 2. with a small amount of concentrated sulphuric acidat room temperature, separating the acid layer, and washing tneremaining polysiloxane layer with water.

A second process comprises the hydrolysis of mixtures of organohalogeno-silanes, one member of which is represented by the formulaRsSlX, and the other members of which are chosen from the class RaSiXa,RSiXa, and sun, wherein R has the meaning herelnbefore indicated and Xrepresents a halogen atom. The product of hydrolysis is likewiseseparated from the acid. In this method of preparation, the averagecomposition of the mixture of hydrolyzable silanes should correspond tothe formula RtSiXu-t where b is substantially greater than 2, preferablygreater than about 2.5, and is less than 3. For maximum yields of thechain compounds, it may be desirable to follow this' hydrolysis processby treatment of all or part of the products 'with sulphuric acid asdescribed briefly above.

A third general process, especially suitable for introducing phenylgroups into the molecule, comprises treating a mixture of anorganodisiloxane of the formula RaSi-O-SIR: and an organo silanediolsuch as diphenyl silanediol (CeHt)2S 1(OH)2 with a small amount ofconcentrated sulphuric acid. Other polysiioxanes of whichoctamethylcyclotetrasiloxane [(CHJMSiOJi boiling at 175 C. is anexample, may be added to the starting materials. Thesecyclopolysiloxanes are more fully described in my copending application8. N. 463,813 filed concurrently herewith and assigned to the sameassignee as the present invention.

A fourth general process comprises bringing together, with or without asolvent. a silanol of the type RaSiOI-I and an organo-halogeno silane ofthe type RrSlXn An alternative procedure is to permit a silanediol ofthe type R2Si(OH)r to react with a monohalide of the type RaSix. Othermore complex silanols in which the presence of Si0H groups is noted, butwhich are so complex as to defy a determination of exact structure, maylikewise be permitted to react with halides of the type nasix. or may becaused to react with disiloxanes of the type RaSi-O-SiRa.

It is to be noted that all four of these general procedures require aspart of the starting material an organo-silicon compound containing,

the group RaSi-, which emerges from the reaction as a terminal siliconatom of the skeletal lubricants as will be described more fully here- 75chain or branched chain structure of the ried out. and describing thenovel compounds so produced. I have chosen comparatively simple,chemically pure starting materials which permit a separation of theindividual products of reaction one from another. Examples of suchsimple starting materials are hexamethyldisiloxane (CH3)sSiOSI(CHa)a,octaphenylcyclotetrasiloxane [(CeHshSiOh. diphenylsilanediol(CcH)2Si(OH)2, hexamethylcyclotrlsiloxane [(CHa)2SiO]3,trimethylchlorosilane (CH3)aSiCl, methyltrichlorosilane CHaSiCls,silicon tetrachloride SiCh, etc.

Exmrs 1 1. Octamethyltrisiloxane 2. Decamethyltetrasiloxane 3.Dodecamethylpentasiloxane 4. Tetradecamethylhexasiloxane The propertiesof these compounds are set forth in the following table in which thecompounds are designated by the above reference numerals.

' Molecular weight Compound Np Found Theory 230 2&6. 4

Representative analyses of are:

these compounds Found Theory is believed to favor the formation of thelower polysiloxane chain compounds. while a decrease in the proportionof disiloxane derivative results in the formation of larger quantitiesof the products of higher molecular weight not readily separated fromeach other by distillation.

The following example illustrates an alternative process for preparingcompounds of this In addition to the compounds listed, some of inventionand likewise illustrates the preparation of simple branched chainderivatives.

EXAMPLE 2 A mixture of methyltrichlorosilane andtrimethylmonochlorosilane in the ratio of 0.67 mol of the former to 2.69mols of the latter compound was hydrolyzed by adding it to 700 c. c. ofviolently stirred water cooled externally so that the maximumtemperature of the reaction mixture was 32 C. Two liquid layers wereformed. The lower aqueous layer was discarded, and the upper layer waswashed with water and dried over anhydrous potassium carbonate. Thisliquid was divided by distillation into three portions: (A) chieflyhexamethyldisiloxane, (B) a fraction boiling up to 200 C. at 1 mm.pressure, and (C) a non-volatile oil. Fractions A and C were recombinedand shaken with a small quantity of sulphuric acid. The oil was thenwashed free of acid with water, dried and distilled'as before, whereuponmore of the (B) fraction was obtained. 0n fractional distillation of theB fractions, the compound Found Theory g 0 38. 43 38. 66 a H- 9. 65 9.74 a Si 35. 36. 15

In addition to methyl tri- (trimethylsiloxy) silane, somehexamethyldisiloxane was isolated, and there remained a relativelynon-volatile oil which contained more complex compounds, the simplest ofwhich were probably compounds of the type H|).sl-o sl-osucm ARCH: n

when n is an integer greater than 1.

The following example illustrates a process for preparing compounds ofthis invention in which the various R's in the general formula arerepresented by different hydrocarbon radicals, and in which a silanediolof the type R2Si(OH)2 is used as one of the starting materials.

EXAMPLE 3 A mixture of hexamethyldisiloxane and diphenylsilanediol inthe proportions of 41 grams of the former to 54 grams of the latter wasagitated with 30 grams of concentrated sulphuric acid for 10 minutes atroom temperature. The

. 7 crystalline diphenylsilanediol is substantially(CHahSi-O-SKCaHsh-HKCIB):

was isolated. This compound has the following properties: B. Pt.172-473" C. at 18 mm., dzo .9728 g./cc., Nu" 1.4927, mol. wt. found 360,theory 360.4.

% H C Si mind 7. 70 58. 25 2%. 45 Theory 7.83 59. 94 23. 55

The residue remaining in the flask was a viscous liquid at roomtemperature, and is presumed to contain complex compounds of the type(CH3) aSi-- [OSi(CsHs) 2] n-SKCHD wherenisgreater than 1.

Example 4 illustrates a further method of preparation of the novelcompounds of this invention, also utilizing diphenylsilanediol.

EXAMPLE 4 Twenty-five grams of diphenylsilanediol dissolved in 325 c. c.of ether was added drop by drop below the surface of 25 g. oftrimethylchlorosilane dissolved in 100 c. c. of ether. The reactionmixture was stirred violently throughout the addition, which required aperiod of one hour. After removal of the ether by distillation, theremaining liquid was fractionally distilled. In addition tohexamethyldisilqxane, a yield of 12% of symmetricall,3-hexamethyl-2-diphenyl trisiloxane was obtained. The residue in theflask was a viscous, high-boiling liquid which is believed to comprise amixture of compounds of the type (CH3) 3SiO--[ (CsHs) 2810-] nSi(CH3) a'the fragments thus formed in new positions,

probably by the momentary formation of esters of sulphuric acid followedby hydrolysis of these esters to form new compounds. This is borne outby the fact that the chemical structure of the new compounds indicatesthat the R groups attached to a given silicon atom are not separatedtherefrom at any time during the reaction, but that the breaking andrecombination of the parts of the starting materials always takes placeat an Si-OSi linkage. When the starting materials are both organohalogenosilanes in the proper proportions, and the reaction is carriedout in water, the reaction is believed to be hydrolysis of the halogenand condensation of any silicols formed resulting in the finalpolysiloxanes. Any cyclic compounds formed during the reaction andcontaining the Si-Si linkage are opened by treatment with sulphuric acidand recondensed with fragments of other compounds having terminalRaSi-zroups to form the desired chain compounds. When one of thestarting materials is a halide and the other is a silanol or silanediol.then the reaction is believed to be a splitting out 83.1301 with thedirect formation of a siloxane Whenever one of the starting materialsconsists of a compound in which two diiierent hydrocarbon radicals areattached to the same silicon atom. the silicon atoms of the resultantcompounds will be similarly substituted. A -repre-' sentative reactionof this type would be that between symmetricaldiphenyltetramethyldisiloxane and a cyclic polymer ofmethylphenylsilanone to form compounds of the formula wherein n is awhole number equal to at least 1.

All of the chain compounds which have been prepared in accordance withthis invention are liquid in form. They are to be distinguished fromother liquid organo silicon compounds comprising carbon, hydrogen,silicon, and oxygen by their unique properties. For example, whereasesters of silicic acid, such as ethyl silicate or esters Of organosubstituted silicic acids, likewise are liquids comprising carbon,hydrogen, silicon and oiwgen, they are susceptible to hydrolysis bywater, often yielding gels or resins. The compounds of the presentinvention are stable toward water. Furthermore, whereas some of thehydrolysis products of organo halogenosilanes described in U. S. Patents2,258,218-222 issued to Eugene G. Rochow are liquid in nature, theyrapidly become resinous on heating, due, as is pointed out in thosepatents, to the fact that they comprise compounds in which the ratio oforganic radicals to silicon atoms is less than 2. The viscous liquids ofthe present invention, in which the ratio is greater than 2, are notreadily converted to resins on heating, but on the contrary, maintaintheir liquid form for long periods of heating, thus enhancing theirsuitability as lubricants or heat transfer media. The simpleorganodisiloxanes of the type RaSi-O-SiRa, among which ishexamethyldisiloxane, are relatively fluid compounds of low viscosityand low boiling point, or if the B group is very large, contain adisproportionate amount of carbon and hydrogen at the expense ofthesilicon and oxygen; whereas the compounds of the present invention,having a ratio of R groups to siliconatoms less than 3, possess thedesirable properties of the siloxane bond in much greater degree.

Certain substituted cyclopolysiloxanes of the general formula [R2Si01nhaving an' oxygen to silicon ratio of 1 which are further described inmy copending application S. N. 463,813 mentioned above, are also liquidsbut they differ from the compounds of the present invention in certainimportant characteristics. For example, octamethylcyclotetrasiloxane anddecamethyltetrasiloxane are similar in chemical composition inrespectively having the formulas (CH3) aSi4Q4 and (CH3)1oSi403, andboiling at C. and 194 C. respectively. Their freezing points. however,differ widely, being 17.5 C. and 68 C., indicat- Properties of cyclicpolymers [(C'Ha) zSiOln Viscosity, Number of Ratio Via, 51 mm B. Pt., c.F. Pt., "0.

Properties of polymers CH:[ (CH3) zSiOhSKC'Ha) a Viscosity, Number ofRatio Vis.

Si Atom 3.1%., c. F. Pt., "0. 1

4 191 B8 1.31 0.69 1.90 5 229 -81 1. 83 0. 93 1. 97 B 1 142 100 2. 37 1.l7 Z. 04

l mm.

Thus it is seen that the linear or straight chain compounds boil higher,freeze lower, have lower viscosities, and have smaller changes inviscosity with temperature than do the corresponding ring compoundscontaining the same number of silicon atoms. The more favorableviscosity index of the chain compounds is even more pronounced whenexamined on a logarithm viscosity-reciprocal temperature char-t. Thesedifierences indicate the superiority of the chain compounds over thering compounds as lubricants, particularly at low temperatures. Owing tothe practical impossibility of separating the individual pure compoundsfrom each other when the value of n is higher than 8 or 10, comparativedata on cornpounds of higher viscosity is not available, but from anexamination of the trends it is believed that, as stated above, thecomparison noted above is valid through the entire series of compounds.

EXAMPLE 5 Preparation cc. Distillate Number cc. A cc.B .c.ethcr .c.H1504 below t The most viscous of all the oils was prepara- 10 tion I,which contained no (CH3) aSi groups. Oils of this type are more fullydescribed and claimed in my copending application 5. N. 463,815 filedconcurrently herewith and assigned to the same assignee as the presentinvention. As is described in that application, such products consistprimarily of cyclic, polymeric dimethyl silanones of the formula (01-11)2310]: wherein a: is an integer greater than 10. This material wouldjust barely flow at room temperature. The most fluid of all was II,which contained the greatest amount of (CH3) :Si groups, and had" aviscosity of about 4 op. The others increased in viscosity as theproportion of (A) was decreased, up to VI, which had about the viscosityof a medium grade motor oil. When kept at the temperature of solidcarbon dioxide (-80 C.) for a day, sample 11 was very fluid. samples IIIand IV were less fluid but would pour. while the remainder of the oilswere more or less crystalline or solid. This example illustrates theeffect of changing the proportion of hexamethyldisiloxane in thestarting material. It is to be noted that although both of the startingmaterials boil below 200 C. they react to form oils substantiallynonvolatile at 300 C., which oils will pour at -80 C. It will also benoted that as the proportions of (A) increased, the final productscontained greater proportions of chain compounds and smaller proportionsof the above-mentioned cyclic compounds resulting in a decrease of thepour points and viscosities of the oily products.

The following example illustrates a method of preparation of an oil ofabout the viscosity of a light motor oil.

Exempt: 6

Ninety-three grams of hexamethyldisiloxane, 593 g. ofoctamethylcyclotetrasiloxane and cc. of concentrated sulphuric acid wereshaken together at room temperature for 20 hours. The

lower acid layer was drawn oil from a separatory funnel and the upperoily layer was washed free of acid with water, fllteredand dried overanhydrous potassium carbonate. A sample of the light oil thus obtainedwas placed in a beaker along with a piece of iron and a piece of copperat a temperature of C. After being continuously exposed to the air atthis elevated temperature for a period of 6 weeks, the oil remainedwater-white in color, did not deposit sludge nor develop acidity, andthe pieces of metal were not corroded. Under the same circumstances apetroleum oil would have deteriorated badly.

During this period of time, from V4 to /3 of the oil evaporated. Inorder to avoid this evaporation, the bulk of the oil was placed in aflask, and /5 of it was distilled out under vacuum. The residue wassomewhat more viscous than the distillate, having the followingviscosities at the indicated temperatures.

At 212 F. the oil had a viscosity of 6.7 cp., which increased to 24 cp.on cooling to 68 F., a 3 to 4 fold increase. A petroleum oil of similarviscosity increased in voscosity from about 4 centistokes at 212 F. toabout 30 centistokes at 68 R, an increase of 7 to 8-fold. This comarison again shows the superiority of the polysiioxane oils overpetroleum oils.

Methylpolysiloxane oils described by this invention are particularlysuitable for lubrication under oxidizing conditions at elevatedtemperatures, at very low temperatures, and in locations where widetemperature fluctuations are experienced.

11 They should be particularly suitable for the lubrication ofinstrument bearings by virtue of their freedom from gum formation. Theyshould likewise be particularly useful in locations where it isinconvenient to continually add lubricant to a hearing or where itisinconvenient to clean it.

Their maintenance of water-white color even under extreme oxidizing andsunlight conditions makes these compounds especially suitable forsofteners or plasticizers for colorless or lightcolored resins or films.

Their stability toward oxidation and discoloration in the presence ofcopper, as well as their freedom from acid-forming tendencies, makesthem particularly suitable for insulating fluids.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Liquid polysiloxanes having the formula R(:+z)SiO(-n whereinthevarious R's represent monovalent hydrocarbon radicals, and a is awhole number equal to at least 3, and in which every oxygen atom issituated between two silicon atoms, every silicon atom is attachedthrough oxygen to at least one other silicon atom, and each terminalsilicon. atom in the SiSi skeletal structure is joined to three Rgroups.

3. A methyl polysiioxane chain compound having the formula R(:a+: SiO(-1wherein R represents a methyl group, a is a whole number equal to atleast 3, the said polysiloxanes being characterized by the fact thatevery oxygen atom wherein R and R represent different monovalenthydrocarbon radicals and n is a whole number equal to at least 1.

5. Liquid organo-silicon compounds having the formula i it 1.

wherein R represents a methyl group, R a phenyl group, and n is a wholenumber equal to at least 1.

6. organo-silicon chain compounds of the formula i i i wherein Rrepresents a monovalent hydrocarbon radical, R, represents a monovalentradical selected from the class consisting of the monovalent radicalsrepresented by R and O-Si-Ra radicals, and n is a whole number and isequal to at least 1, the said compounds being stable liquids at roomtemperature.

7. Methyl tri- (trimethylsiloxy)'silane having the formula- RRgSl-O-l-O-BiB;

wherein R represents a methyl group, the said silane being a liquidboiling at approximate] C.

8. Octamethyltrisiloxane.

9. Symmetrical 1,3-hexamethyl-Z-diphenyltrisiloxane.

10. The method of preparing a liquid polysiloxane which comprisesforming a mixture of compounds of the formula RsSlOSlRa and wherein theR's represent monovalent hydrocarbon radicals and a: is a whole numberequal to at least 3, treating said mixture with concentrated sulphuricacid and washing the treated products free of acid.

11. The process of preparing liquid polysiloxane chain compounds havingthe general formula R(2a+2)SiaO(a-1) wherein R represents a monovalenthydrocarbon radical and a is a whole number and is equal to at least 3which comprises hydrolyzing a mixture of organo halogenasilanes havingthe average formula RbSiX(4-b) where X represents a chlorine atom and bis a number substantially greater than 2 and less than 3, washing thehydrolysis products with water, drying the washed products and treatingthe dried products with sulphuric acid.

12. The process of preparing liquid organosilicon compounds having theformula wherein the various (R)s represent monovalent hydrocarbonradicals and n is a whole number and is equal to at least 1, whichcomprises treating a mixture of an organodisiloxane of the formulaR3SiOSiR3 and a cyclic organo-silicon polymer having the formula [RzSiOhwherein the various Rs have the meanings above indicated and a: is awhole number and is equal to at least 3 with concentrated sulphuric acidat room temperature.

13. The process of preparing liquid methyl silicon compounds of theformula (CH3) 3Si[OSi(CHa) aInOSKCII's):

wherein n is a whole number and is equal to at least one, whichcomprises treating a mixture of hexamethyldisiloxane and a cyclicpolymer of dimethyl silanone with concentrated sulphuric acid andthereafter washing the reaction products to remove the acid.

14. The process of preparing liquid methyl phenyl siloxanes having theformula (CH3) 3 [OSKCsI-Is) alaOSi (CH3) 3 wherein n is a whole numberand is equal to at least one, which comprises treating a mixture ofhexamethyldisiloxane and diphenylsilanediol with sulphuric acid andwashing the reaction products with water to remove the acid.

15. A composition of matter comprising a liq- 13 uid mixture of methylpolysiloxane branched chain compounds of the formula (CH3) washout-1wherein a is a whole number equal to at least 3 and,in which everyoxygen atom is situated between two silicon atoms, every silicon atom isattached through oxygen to at least one other silicon atom, and eachterminal silicon atom in the Si-O-Si skeletal structure is Joined tothree methyl groups, at least some of the silicon atoms in saidpolysiloxane compounds being connected through oxygen to three othersilicon atoms.

16. A composition of matter comprising a liquid mixture of methylpolysiloxanes having the formula (CH3)2a+2siao(0-1) wherein a is a wholenumber equal to at least 3 and in which every oxygen atom is situatedbetween two silicon atoms, every silicon atom is attached through oxygento at least one other silicon atom, and

each terminal silicon atom in the Si-O-Si skeletal structure is joinedto three methyl groups, the said mixture including branched chain methylpolysiloxanes wherein some of the silicon atoms are connected to threeoxygen atoms.

17. A liquid mixture of methyl polysiloxanes boiling about 300 C. andhaving the formula (CH3)2a+2SiaO(a-1) wherein a is a whole numbergreater than 5 and in which each oxygen atom is situated between twosilicon atoms, each silicon atom is attached through oxygen to at leastone other silicon atom, and each terminal silicon atom is joined tothree methyl groups.

18. A liquid composition of matter comprising a liquid mixture of organopolysiloxanes having the formula R(2a+z)S1aO(a-1) wherein R represents amethyl radical, and a is a whole number equal to at least 3 and in whichevery oxygen atom is situated between two silicon atoms, every siliconatom is attached through oxygen to at least one other silicon atom, andeach terminal silicon atom in the Si-O-Si skeletal structure is joinedto three R groups.

19. Liquid organo-siloxanes of the formula CH: CH;

wherein n is a positive integer.

sitive integer. 6O

- "i4 21. Liquid organo-siloxanes corresponding to the formula R R R" RSi O i 0Si -R" R L nl IJ RII where R, R and R" each represents amonovalent hydrocarbon radical, at least one B. and at least one R" eachbeing a methyl radical, at least one R being a phenyl radical, and nrepresents a positive integer.

23. The method of interacting a liquid polymeric organo-siloxane whosestructural units correspond substantially to the formula RzSiO and anorgano-siloxane having the general formula RaSiOSiRa, where each Itrepresents a monovalent hydrocarbon radical,- which comprises treating amixture of said siloxanes with a strong acid.

24. The method which comprises treating a mixture ofhexamethyldisiloxane and a liquid polymeric dimethyl silicone with astrong acid.

WINTON I. PATNODE.

REFERENCES CITED The following references are of recordin the file ofthis patent:

UNITED STATES PATENTS Name Date Lincoln Sept. 6, 1938 Rochow Oct. 7,1941 OTHER REFERENCES Ladenburg, Annalen," vol. 164, pages 325-328.

Kipping, fJ. Chem. 800.," vol. 79, pages 455-458.

Burk, Polymerization," 1937, pages 62-64.

Hyde, Jour. Am. Chem. Soc.," vol. 63, pages 1194-1196 (1941).

Martin and Kipping, "Jour. Chem. Soc." (London) vol. 95, pages 313-4(1909).

Stock, "Chem. Abstracts, vol.v 13, page 2536.

Rochow, Jour. Am. Chem. 500.," vol. 63, pages 798-800 (1941).

Emeleus, "Jour. Chem. Society," London (1944) pages 454-456.

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